This application claims the benefit of Korean Application No. 6359/1999 filed Feb. 25, 1999, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a chemical vapor deposition device, and particularly, to a gas injection system for a chemical vapor deposition device. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for improving process performance by facilitating temperature control at a shower head unit and by restricting generation of particles causing contamination, and evenly providing gas at a surface of a wafer.
2. Description of the Related Art
In order to form a BST [(Ba,Sr)TiO3] thin film, gas phases of barium, strontium, titanium, and oxygen are provided at a surface of a wafer positioned in a chamber, and chemical reactions of the gases.
Constitution of a conventional CVD device is described with reference to the accompanying drawings.
FIG. 1 is a schematic view illustrating the conventional CVD device including a chamber 10 having a space of a predetermined size, a heater casing 20 provided in the chamber 10, a heater 30 provided in the heater casing 20, a wafer 40 positioned at the upper portion of the heater casing 20, and a shower head unit 70 engaged with a gas providing pipe and having a nozzle plate 60 for injecting gases on the wafer 50. Additionally, an exhaust pipe (not shown) engaged with the chamber 10 is provided for externally discharging the gases from the chamber 10. There are also provided an exhaust pipe (not shown) and a vacuum pump (not shown) for producing a vacuum inside the chamber 10.
The shower head unit 70 for a gas injection will now be explained in more detail with reference to FIGS. 2 through 5.
FIG. 2 is a partial cross-sectional view illustrating the shower head unit 70. FIGS. 3 and 4 are a front view and a cross-sectional view respectively illustrating the nozzle plate 60 positioned at the bottom portion of the shower head unit 70. FIG. 5 is an enlarged view of portion II in FIG. 4.
At the upper portion of the shower head unit 70, a heater 71 is provided for maintaining the gases (barium, strontium, titanium and oxygen) provided through the gas providing pipe 50 at an elevated temperature. In addition, a buffer space 72 is formed inside the shower head unit 70 in order for the gases to be widely diffused. The nozzle plate 60 for evenly injecting the gases on the wafer 40 is provided at the bottom portion of the buffer space 72. Here, a plurality of nozzles 61 are formed at the nozzle plate 60 in order to evenly inject the gases on the wafer 40.
Operation of the conventional CVD device will now be described.
Firstly, the wafer 40 is positioned at the upper portion of the heater casing 20 in the chamber 10 by a wafer transfer (not shown). The chamber 10 is under a vacuum condition maintained by a vacuum pump (not shown). Thereafter, the gases (barium, strontium, titanium, and oxygen) having a predetermined temperature are introduced into the shower head unit 70 through the gas providing pipe 50 and widely diffused in the buffer space 72.
Here, the gases diffused in the buffer space 72 of the shower head unit 70 are maintained at a predetermined temperature by the heater 71. The diffused gases are injected onto the wafer 40 through the plurality of nozzles 61 of the nozzle plate 60. On the other hand, a temperature of the wafer 40 positioned at the upper portion of the heater casing 20 is increased to approximately 500xc2x0 C. by the heater 30. Accordingly, the gases in the chamber 10, such as barium, strontium, titanium, and oxygen are mixed and reacted one another. As a result, a resultant material is deposited at the surface of the wafer 40, thereby forming a BST thin film.
The heater 30 has a higher temperature than the wafer 40 in order to increase its temperature. However, in the gas injection system for the conventional CVD device, a radiant heat of the heater 30 is transmitted into the shower head unit 70, thus increasing a temperature of the shower head unit 70. As a result, the temperature of the gases become higher than a desired temperature. Therefore, the gases are partially reacted in the buffer space 72 of the shower head unit 70. Also, a chemical reaction does not start on the wafer but in the shower head unit 70, thereby generating particles that are a main cause of contamination. As a result, it reduced the process performance.
In order to overcome such a disadvantage, the nozzle plate 60 of the shower head unit 70 must be positioned separately from the wafer 40 by a predetermined distance. However, such a modification creates another problem because it is difficult to keep the size of the CVD device at a minimum.
Accordingly, the present invention is directed to a gas injection system for chemical vapor deposition device that substantially eliminates one or more of problems due to limitations and disadvantages of the related art.
Another object of the present invention is to provide a gas injection system for a chemical vapor deposition (CVD) device which can restrict generation of particles causing contamination by facilitating a temperature control of a shower head unit in regard to gases sensitive to the temperature, and which can improve process performance.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a gas injection system for a chemical vapor deposition (CVD) device includes a gas providing pipe providing gases into the system, a shower head-unit coupled to the gas providing pipe for evenly injecting the gases on a wafer, and a temperature control unit coupled to the shower head unit for controlling a temperature of the shower head unit.
In another aspect of the present invention, a gas injection system for a chemical vapor deposition (CVD) device includes a gas providing pipe providing gases into the system, a shower head unit coupled to the gas providing pipe for evenly injecting the gases on a wafer, a heating system coupled to the shower head unit for controlling a temperature of the shower head unit, a cooling system coupled to the heating system for controlling a temperature of the heating system, and a temperature sensor coupled to the shower head unit.
It is to be understood that both. the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed.